Deprecated assertEquals (and similar methods) don't work in marbles

* marbles.core version: 0.9.5
* marbles.mixins version: 0.9.5
* Python version: 3.6.5
* Operating System: Linux

### Description

Tried to run a `unittest` test that uses the deprecated name `assertEquals` instead of `assertEqual`.

### What I Did

```
import marbles.core

class MyTestCase(marbles.core.TestCase):

def test_assertEqual_success(self):
x = 1
y = 1
self.assertEqual(x, y)

def test_assertEqual_failure(self):
x = 1
y = 2
self.assertEqual(x, y)

def test_assertEquals_success(self):
x = 1
y = 1
self.assertEquals(x, y)

def test_assertEquals_failure(self):
x = 1
y = 2
self.assertEquals(x, y)
```

The `assertEquals` tests fail with the following stack:

```
======================================================================
ERROR: test_deprecated_assertEquals_failure (tests.test_marbles.InterfaceTestCase) (use_annotated_test_case=False)
Does the deprecated assertEquals method work on failure?
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/leif/git/marbles/marbles/core/tests/test_marbles.py", line 373, in test_deprecated_assertEquals_failure
self.case.test_deprecated_assertEquals_failure()
File "/home/leif/git/marbles/marbles/core/tests/test_marbles.py", line 93, in test_deprecated_assertEquals_failure
self.assertEquals(x, y)
File "/home/leif/git/marbles/marbles/core/marbles/core/marbles.py", line 538, in wrapper
return attr(*args, msg=annotation, **kwargs)
File "/usr/lib64/python3.6/unittest/case.py", line 1323, in deprecated_func
return original_func(*args, **kwargs)
TypeError: assertEqual() missing 1 required positional argument: 'second'

======================================================================
ERROR: test_deprecated_assertEquals_success (tests.test_marbles.InterfaceTestCase) (use_annotated_test_case=False)
Does the deprecated assertEquals method still work?
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/leif/git/marbles/marbles/core/tests/test_marbles.py", line 364, in test_deprecated_assertEquals_success
self.case.test_deprecated_assertEquals_success()
File "/home/leif/git/marbles/marbles/core/tests/test_marbles.py", line 88, in test_deprecated_assertEquals_success
self.assertEquals(x, y)
File "/home/leif/git/marbles/marbles/core/marbles/core/marbles.py", line 538, in wrapper
return attr(*args, msg=annotation, **kwargs)
File "/usr/lib64/python3.6/unittest/case.py", line 1323, in deprecated_func
return original_func(*args, **kwargs)
TypeError: assertEqual() missing 1 required positional argument: 'second'

----------------------------------------------------------------------

```

### Expected behavior
I expected `assertEqual` and `assertEquals` to behave the same. Instead, `assertEqual` does the expected thing, while `assertEquals` fails with a `TypeError`